I was told there was something wrong with the calculation, but didn't really get a proper explanation of why. I'm quite sure that the first two lines are right, and the answer should be too. So that really only leaves the third row

x^2 + 2x = (1)(x^2 + 2x) + 0

But it's really simple, so how could it be wrong.. It drives me mad :confused:

Oh, and I noticed I wrote 2^x instead of 2x in the initial description, it should be 2x as in the calculation. Sorry about that.